286 Hand-riveting and Caulking. The Plater requires three chisels—the flat chisel, Fig. 201, the cross-cut, as at Fig. 200, and another with curved profile for chipping the edges of manholes, &c. Hammers are of three kinds;—the fitter's hammer, Fig. 199, the sledge hammer, and a riveting hammer with long head and small panes for places where the sledge or the portable riveter cannot be employed. A Riveting Gang consists of three men and a boy ; the boy brings the red-hot rivet, which the leader inserts, as at r>, Fig. 279 • another man holds up the dolly, as at A; while the third man and leader give alternating blows until the cheese head E is formed. The leader then applies the cupping tool or snap B, while the striker gives two or three smart finishing blows with the sledge c. Work should be designed for machine-riveting wherever possible, as hand work can neither make the rivet com- pletely fill the hole or compete in cost.* Before riveting a seam, the plates, if punched or drilled separately, are brought into alignment by the podger and bolted in one or two places; then the drift at A, Fig. 280, may be applied and forced through by a hammer to clear out the holes. Though of undoubted advantage if used temperately, the drift is now banished from the best shops, plates being injuriously dis- tressed by it when the holes are very untrue. When a joint is to be broken, the rivet-heads are chopped off by the set B, struck with a sledge, and the punch c applied to drive out the rivet 1 Caulking is the process of making a boiler joint thoroughly staunch by burring up the plate edges with a blunt chisel or caulking tool. In Fig. 281, A is the section of a boiler joint, where the edge of the outer plate is bevelled at an inclination of i in 8. Striking the tool B with a hand hammer a burr is formed, and the rivet heads treated similarly, as at a. Severe caulking with sledge diminishes the grip of the rivet and frictional strength of the joint To avoid this a Mlering tool c is often used, but there is no objection to caulking if a large number of light blows be given. A Pneumatic Caulker will be described later. Caulking the rivets is not considered necessary If hydjr&ulic riveting be properly applied. (See f. 322, also Appendices IL md IVn$p. 826 and 949) * See diagrams by Mr. Tweddell, prepared for his paper before the North- east Coast Institution of Engineers and Ship-builders, p. 321.